A hybrid vehicle incorporating an engine and an electric motor as a driving source is known. The hybrid vehicle has a power storage device such as a battery for storing electric power to be supplied to the electric motor. The battery is charged with electric power generated by a power generator driven by the engine, electric power regenerated with the electric motor during deceleration of the vehicle, and the like.
Such a hybrid vehicle can run using either one or both of the engine and the electric motor as a driving source, depending on an operating state and the like of the vehicle. Thus, for example, when an accelerator pedal position is small, the engine is stopped, and the vehicle can run using only the electric motor as a driving source. When sudden acceleration is required, on the other hand, the engine is driven in order to obtain desired acceleration.
A running state in which the engine is stopped and only the electric motor is used as a driving source involves no exhaust gas emissions, thus imposing only a small environmental load. In a hybrid vehicle, however, stopping and starting of an engine may be repeated as described above. As a result, the engine may be stopped before the completion of warm-up. Therefore, the engine may be frequently re-started with the warm-up uncompleted. As is well known, when an engine is started before the completion of warm-up, a relatively large amount of HC or CO may be exhausted.
In view of this problem, Japanese Patent Laying-Open No. 2010-58746 (PTL1) discloses, in claim 3 and the like, that where the temperature of the catalyst is lower than a prescribed value, even though a request for electric running to stop the internal combustion engine and use mechanical power of the rotating electric machine is made, the request for electric running is not permitted.